Field of the Disclosure
This disclosure relates to superconductors, specifically to improving the mechanical and electrical properties of superconducting tapes.
Background of the Disclosure
Several materials and systems are being researched in order to solve the looming problems with energy generation, transmission, conversion, storage, and use. Superconductors may be a unique system solution across a broad spectrum of energy problems. More specifically, superconductors enable high efficiencies in generators, power transmission cables, motors, transformers and energy storage. Further, superconductors transcend applications beyond energy to medicine, particle physics, communications, and transportation. Superconducting having epitaxial, single-crystal-like thin films on polycrystalline substrates are currently being developed.
There are about nine components in a typical second-generation (2G) high-temperature superconducting (HTS) tape. The architecture consists of several oxide films on a metallic substrate and capped with silver and copper over-layers. The composite structure is prone to issues such as debonding between individual layers and delamination within the superconductor layer. Transverse tensile strength measurements on some conventional 2G HTS tapes, wherein a tensile stress is applied normal to the tape's surface, have shown evidence of weakness, although transverse tensile measurement experiments are themselves prone to non-uniform stress states which may render the validity of the obtained data questionable. A uniform pull or stress may be imparted on the tape by means of Lorentz force acting mutually or mutually applied perpendicular to a transport current flowing through a superconducting tape in conjunction with an externally applied magnetic field. The fracture surfaces of the 2G HTS tape provide insight into the interfaces and films architecture or structures that are prone to debonding and delamination. More specifically, the interface between the LaMnO3 (LMO) top buffer layer and the REBa2Cu3Ox (REBCO) superconducting film is prone to debonding, and the REBCO itself is prone to delamination within the overall architecture of the HTS tape.
Additionally evidence of weak transverse strength in tapes in coils fabricated with epoxy impregnation has been observed. The difference in thermal expansion coefficients of the tape and epoxy may result in the transverse stress on the tape. Thus, if the tolerance of the tape to this stress is low, then coil degradation may occur. Further, as a significant proportion of the applications of present-day 2G HTS tape involve coil geometries, this mechanical weakness poses a significant problem in the deployment of 2G HTS tapes to these industries.
Thus, there is a demand for a HTS tape having improved transverse tensile strength and electrical properties for commercial applications.